RCM parallel robot mechanism with three motion modes

Abstract

The RCM parallel robot mechanism with the three motion modes is simple in structure, convenient to machine, high in rigidity and suitable for more scenes. A moving pair of a moving platform and a rotating pair of a branch chain are combined together to serve as a connecting structure of the moving platform and the top end of the branch chain, the position of the rotating pair at the top end of the branch chain is changed by adjusting the moving pair, the position relation among the axes of the rotating pair at the top end of the branch chain is controlled, and the relation between the axes of the rotating pair at the top end of the branch chain and a fixed platform is controlled. Therefore, three different motion modes are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mechanism and robot technology, in particular to a RCM parallel robot mechanism with three motion modes. BACKGROUND

[0002] The end effector of a surgical instrument for minimally invasive surgery can move based on a remote center point, which is called a remote center mechanism, and the movement is called remote center motion. Most remote center parallel mechanisms have a single degree of freedom, which lacks versatility. For example, if a patient only needs a simple puncture surgery, a 1R1T degree of freedom end effector can complete the surgery. If a multi-degree of freedom end effector is used, the difficulty of the surgery will increase. If a complex surgery is performed, a single degree of freedom end effector cannot meet the demand.

[0003] Skilled persons will need to introduce the reconfigurable concept into the RCM mechanism to achieve a RCM mechanism with multiple degrees of freedom. Due to different surgical needs, a reconfigurable RCM (Remote Center of Motion) parallel mechanism can perform multiple surgeries without assembly. Existing reconfigurable parallel robots, such as the patent with publication number CN109009448A, disclose a parallel surgical robot with a remote center of motion, but it uses an arc-shaped guide rail to achieve RCM. The arc-shaped guide rail is difficult to manufacture and has low rigidity. From the perspectives of structural complexity and cost, the application scenarios are limited. SUMMARY

[0004] In order to solve the problem that the existing RCM parallel robot structure is difficult to process and has low rigidity, resulting in limited application scenarios, the present application provides a RCM parallel robot mechanism with three motion modes, which has a simple structure, is easy to process, has high rigidity, and is suitable for more scenes.

[0005] The technical solution of the present application is as follows: a RCM parallel robot mechanism with three motion modes, comprising: a fixed base and a moving platform, characterized in that: the fixed base and the moving platform are connected by N parallel branches, wherein N is greater than or equal to 3; all the branches have the same branch structure, which is an RRRRR branch; The moving platform comprises N equal-length moving platform links; the moving platform link is a plate structure with a through slot in the middle as a moving platform sliding groove; at least one end of the moving platform link is provided in a circular arc shape; the upper surface of the circular arc end is convex upward along the arc of the end and perpendicular to the plate surface of the moving platform link, and the lower surface of the circular arc end is provided with a concave circular arc sliding groove along the arc of the end; the shape and size of the circular arc sliding groove are adapted to the shape and size of the circular arc slider; The moving platform comprises N moving platform rotary pairs and N moving pairs; N moving platform links are inserted together from top to bottom based on the circular arc-shaped sliding grooves and the circular arc-shaped sliding blocks, forming N coaxial moving platform rotary pairs; The top end of each branch chain is connected to the moving platform based on a moving pair, and the bottom end is connected to the fixed base based on the bottom rotary pair; the branch chains are evenly arranged on the circumference formed by the connection points of the bottom ends of the branch chains and the fixed base; The intersection of the rotation axes of the bottom rotary pairs of the N branch chains is the telecentric point.

[0006] It further comprises: The structure of the branch chain comprises four branch chain links connected in sequence from bottom to top: a first link, a second link, a third link, and a fourth link; One end of the first link forms a first rotary pair with the fixed base, the other end forms a second rotary pair with one end of the second link, the other end of the second link forms a third rotary pair with one end of the third link, and the other end of the third link forms a fourth rotary pair with one end of the fourth link; the other end of the fourth link is provided with a protruding cylindrical columnar sliding block with a diameter matching the size of the moving platform sliding groove opened on the moving platform link; the columnar sliding block is movably inserted into the moving platform sliding groove, forming the moving pair of the moving platform and also forming a fifth rotary pair of the branch chain; The rotation axes of the second rotary pair, the third rotary pair, and the fourth rotary pair are parallel to each other; The rotation axes of the first rotary pair and the fifth rotary pair are neither parallel nor collinear to each other; at the same time, the rotation axes of the first rotary pair and the fifth rotary pair are perpendicular to the rotation axes of the second rotary pair, the third rotary pair, and the fourth rotary pair, respectively; The rotation axis of the moving platform rotary pair is perpendicular to the plane where the moving platform is located; It further comprises a driving pair, which comprises a moving platform variant driving pair and a branch chain driving pair; The moving platform driving pair comprises N moving pairs; The branch chain driving pair comprises the first rotary pair and the second rotary pair on each branch chain; The structure of the first link comprises a ring-shaped connector, a one-letter connector, and a rod body; the one-letter connector is arranged at one end of the rod body in a direction perpendicular to the rod body, and the ring-shaped connector is arranged at the other end of the rod body; the axis of the ring-shaped connector is perpendicular to both the rod body and the one-letter connector; The mechanism of the second connecting rod and the third connecting rod is the same, which comprises a U-shaped connector, a straight-shaped connector and a rod body, one end of the rod body is provided with a closed end of the U-shaped connector, two open ends of the U-shaped connector are provided with through holes in a direction perpendicular to the rod body, and the straight-shaped connector is arranged at the other end of the rod body in a direction parallel to the axes of the two through holes; and the diameter of the straight-shaped connector is adapted to the inner diameter of the through hole; The fourth connecting rod further comprises a rod body and a U-shaped connector, one end of the rod body is provided with a closed end of the U-shaped connector, two open ends of the U-shaped connector are provided with through holes in a direction perpendicular to the rod body, and the slider is perpendicular to the rod body and the axes of the two through holes; The fixed base is a cross structure, a star structure, a frame structure or a circular ring structure; The fixed base is provided with a U-shaped connector, a closed end of the U-shaped connector is connected to the fixed base, two open ends of the U-shaped connector are provided with horizontal shafts in a direction parallel to the plane on which the fixed base is located, and the diameter of the horizontal shaft is adapted to the inner diameter of the ring-shaped connector on the first connecting rod; The number N of the branched chains is 4.

[0007] The parallel robot mechanism with three motion modes RCM provided by the application combines the moving pairs of the moving platform and the rotating pairs of the branched chains together and uses them as the connecting structure of the top of the branched chains and the moving platform, the position of the rotating pairs of the top of the branched chains is changed by adjusting the moving pairs, the positional relationship among the axes of the rotating pairs of the top of the branched chains is controlled, and the relationship between the axes of the rotating pairs of the top of the branched chains and the fixed platform is controlled, so that three different motion modes are realized, which are three rotating pairs, one moving pair and having a remote center point, two rotating pairs, three rotating pairs and having a remote center point, and one rotating pair, one moving pair and having a remote center point. The application can realize the reconstruction of the motion mode without changing the internal moving pairs of the branched chains, so that the complexity of the mode reconstruction is reduced. Based on the three-mode parallel mechanism in the application, the motion mode switching method is easy to control, only uses single-degree-of-freedom moving pairs, does not use complex moving pairs, has low requirements for the rigidity of the mechanism components and the assembly precision, has a simple structure, is easy to modularize and process and manufacture, and can be applied to production and assembly operation task scenes that require multiple motion modes. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a schematic diagram of the overall structure of the application; Figure 2 is a schematic diagram of the structure of the first branched chain; Figure 3 is a schematic diagram of the structure of the moving platform; Figure 4 is a schematic diagram of the structure of the connecting rod of the moving platform; Figure 5 Structure diagram of the first connecting rod; Figure 6 Structure diagram of the second connecting rod; Figure 7 Structure diagram of the fourth connecting rod; Figure 8 General posture example of the mechanism of the present application in mode one; Figure 9 General posture example of the mechanism of the present application in mode two; Figure 10 General posture example of the mechanism of the present application in mode three.

[0009] In the figure: 1 first branch chain; 11 first branch chain first connecting rod; 12 first branch chain second connecting rod; 13 first branch chain third connecting rod; 14 first branch chain fourth connecting rod; 2 second branch chain; 21 second branch chain first connecting rod; 22 second branch chain second connecting rod; 23 second branch chain third connecting rod; 24 second branch chain fourth connecting rod; 3 third branch chain; 31 third branch chain first connecting rod; 32 third branch chain second connecting rod; 33 third branch chain third connecting rod; 34 third branch chain fourth connecting rod; 4 fourth branch chain; 41 fourth branch chain first connecting rod; 42 fourth branch chain second connecting rod; 43 fourth branch chain third connecting rod; 44 fourth branch chain fourth connecting rod; 5 reconfigurable mobile platform; 51 mobile platform first connecting rod; 52 mobile platform second connecting rod; 53 mobile platform third connecting rod; 54 mobile platform fourth connecting rod; 511 mobile platform connecting rod body; 512 mobile platform sliding groove; 513 support arc plate; 514 circular arc type sliding block; 515 circular arc type sliding groove; 6 fixed base; 61 base U-shaped connecting head; 7 rod body; 8 letter type joint; 9 ring-shaped connecting head; 10 U-shaped connecting head; 101 through hole; 102 columnar sliding block; 1-1 first branch chain first rotary pair, 1-2 first branch chain second rotary pair, 1-3 first branch chain third rotary pair, 1-4 first branch chain fourth rotary pair, 1-5 first branch chain fifth rotary pair; 2-1 second branch chain first rotary pair; 3-1 third branch chain first rotary pair; 4-1 fourth branch chain first rotary pair; 2-2 second branch chain second rotary pair; 3-2 third branch chain second rotary pair; 4-2 fourth branch chain second rotary pair; 51-1 mobile platform rotary pair one, 52-1 mobile platform rotary pair two, 53-1 mobile platform rotary pair three, 54-1 mobile platform rotary pair four; 51-2 moving pair one, 52-2 moving pair two, 53-2 moving pair three, 54-2 moving pair four. DETAILED DESCRIPTION

[0010] As Figure 1As shown, the application includes a parallel robot mechanism with three motion mode RCM, which includes a fixed base 6 and a reconfigurable moving platform 5. The fixed base 6 and the moving platform 5 are connected by N parallel chains, where N≥3; in this embodiment, the number of chains N is 4, and a total of 4 chains are provided, which are: the first chain 1, the second chain 2, the third chain 3, and the fourth chain 4.

[0011] As shown in Figure 3 and Figure 4 , the moving platform 5 includes N equal-length moving platform links. The number of moving platform links is the same as the number of chains, and in this embodiment, 4 moving platform links are provided, which are: the moving platform first link 51, the moving platform second link 52, the moving platform third link 53, and the moving platform fourth link 54. The moving platform links have the same structure, as shown in Figure 4 , for example, the moving platform first link 51 is used to illustrate the structure of the moving platform link.

[0012] The moving platform link includes a plate-shaped moving platform link body 511, and a moving platform sliding groove 512 is formed in the middle of the moving platform link body 511. At least one end of the moving platform link body 511 is provided in a circular arc shape, and in this embodiment, both ends of the moving platform link body 511 are provided in a circular arc shape, and the length direction of both ends of the moving platform sliding groove 512 is also provided in a semicircular arc shape. The upper surface of one circular arc end of the moving platform link body 511 is provided with a support arc plate 513 protruding upward along the arc shape of the end, the support arc plate 513 is perpendicular to the moving platform link plate, and the top end of the support arc plate 513 is provided with a circular arc-shaped sliding block 514, and the lower surface of the circular arc end of the support arc plate 513 is provided with a concave circular arc-shaped sliding groove 515 along the arc shape of the end. The shape and size of the circular arc-shaped sliding groove 515 are adapted to the shape and size of the circular arc-shaped sliding block 514.

[0013] The moving platform 5 includes N moving platform rotary pairs and N moving pairs; N moving platform links are inserted together from top to bottom based on the circular arc-shaped sliding groove 515 and the circular arc-shaped sliding block 514, forming N coaxial moving platform rotary pairs. In this embodiment, the moving platform rotary pairs have a total of four, which are: the moving platform rotary pair one 51-1, the moving platform rotary pair two 52-1, the moving platform rotary pair three 53-1, and the moving platform rotary pair four 54-1. The moving platform rotary pairs are coaxial rotary pairs, and the rotary shafts of the moving platform rotary pairs are perpendicular to the plane of the moving platform 5.

[0014] All chain structures of the chains are the same, and all the chains are symmetrically distributed on the fixed base 6 in the initial position, where R represents a rotary pair.

[0015] The structure of the chain includes four chain links connected in turn from bottom to top: the first link, the second link, the third link, and the fourth link.

[0016] As shown in Figure 5 , the structure of the first connecting rod includes a ring-shaped connector 9, a linear connector 8 and a rod body 7, the linear connector 8 is arranged at one end of the rod body 7 in a direction perpendicular to the rod body 7, the ring-shaped connector 9 is arranged at the other end of the rod body 7, and the axis of the ring-shaped connector 9 is perpendicular to both the rod body 7 and the linear connector 8.

[0017] The mechanisms of the second connecting rod and the third connecting rod are the same. As shown in Figure 6 , the structure of the second connecting rod is taken as an example to illustrate, which includes a U-shaped connector 10, a linear connector 8 and a rod body 7, one end of the rod body 7 is arranged with the closed end of the U-shaped connector 10, and two open ends of the U-shaped connector 10 are arranged with through holes 101 in a direction perpendicular to the rod body 7; the linear connector 8 is arranged at the other end of the rod body 7 in a direction parallel to the axes of the two through holes 101; the diameter of the linear connector 8 is adapted to the inner diameter of the through holes 101.

[0018] As shown in Figure 7 , the fourth connecting rod includes a rod body 7, a U-shaped connector 10 and a cylindrical columnar slider 102, one end of the rod body 7 is arranged with the closed end of the U-shaped connector 10, two open ends of the U-shaped connector 10 are arranged with through holes 101 in a direction perpendicular to the rod body 7, and the slider is perpendicular to both the rod body 7 and the axes of the two through holes 101. The diameter of the columnar slider 102 is adapted to the size of the moving platform sliding groove 512 arranged on the moving platform connecting rod.

[0019] The connection mode of the branch chain and the fixed base 6 is that a base U-shaped connector 61 is arranged on the fixed base 6, the closed end of the base U-shaped connector 61 is fixed to the fixed base 6, and the two open ends of the base U-shaped connector 61 are arranged with horizontal shafts (not marked in the figure) in a direction parallel to the plane where the fixed base 6 is located, the diameter of the horizontal shafts is adapted to the inner diameter size of the ring-shaped connector 9 on the first connecting rod; the ring-shaped connector 9 on the first connecting rod of each connecting rod is sleeved on the horizontal shafts to form the first rotary pair of each branch chain, thereby realizing the connection between the bottom of the branch chain and the fixed base 6.

[0020] The connection mode of the branch chain and the moving platform 5 is that the columnar slider 102 on the fourth connecting rod is inserted into the moving platform sliding groove 512 from top to bottom to form the moving pair of the moving platform 5 and also form the fifth rotary pair of each branch chain. In this application, the moving pair of the moving platform and the rotary pair of the branch chain are combined together and used as the connection structure between the moving platform and the top of the branch chain through structural design.

[0021] The connection between the four connecting rods of the branch chain, the connection between the branch chain and the moving platform, and the connection between the branch chain and the fixed base are the same, as shown in Figure 2 , the first branch chain 1 is taken as an example to illustrate.

[0022] The annular connector of the first chain first connecting rod 11 and the fixed base 6 form a first chain first rotary pair 1-1; the character-shaped connector of the first chain first connecting rod 11 and the U-shaped connector of the first chain second connecting rod 12 form a first chain second rotary pair 1-2; the character-shaped connector of the first chain second connecting rod 12 and the U-shaped connector of the first chain third connecting rod 13 form a first chain third rotary pair 1-3; the character-shaped connector of the first chain third connecting rod 13 and the U-shaped connector of the first chain fourth connecting rod 14 form a first chain fourth rotary pair 1-4; the cylindrical columnar slider 102 of the first chain fourth connecting rod 14 is movably inserted into the movable platform sliding groove 512 formed in the movable platform connecting rod body 511, forming the moving pair 51-2 of the movable platform 5, and also forming the first chain fifth rotary pair 1-5 of the branch chain.

[0023] The rotation axes of the second rotary pair, the third rotary pair and the fourth rotary pair in each branch chain are parallel to each other; the rotation axes of the first rotary pair and the fifth rotary pair are not parallel to each other nor collinear; at the same time, the rotation axes of the first rotary pair and the fifth rotary pair are perpendicular to the rotation axes of the second rotary pair, the third rotary pair and the fourth rotary pair. As shown in Figure 2 The rotation axes of the first chain second rotary pair 1-2, the first chain third rotary pair 1-3 and the first chain fourth rotary pair 1-4 are parallel to each other; the rotation axis of the first chain first rotary pair 1-1 is perpendicular to the rotation axes of the first chain second rotary pair 1-2, the first chain third rotary pair 1-3 and the first chain fourth rotary pair 1-4; the first chain fifth rotary pair 1-5 is perpendicular to the rotation axes of the first chain second rotary pair 1-2, the first chain third rotary pair 1-3 and the first chain fourth rotary pair 1-4; at the same time, the rotation axes of the first chain fifth rotary pair 1-5 and the first chain first rotary pair 1-1 are not parallel to each other nor collinear.

[0024] In specific applications, in order to ensure that the fifth rotary pair of each branch chain and the moving pair of the movable platform 5 can be realized, the height difference between the support arc plate and the movable platform connecting rod body should be greater than or equal to the thickness of the fourth connecting rod body 7; at the same time, the thickness of the columnar slider 102 should be adapted to the depth of the movable platform sliding groove 512, so as to ensure that the upper and lower stacked fourth connecting rods will not affect each other during sliding and rotating, and to ensure that the columnar slider 102 of each branch can move to the center point position of the movable platform 5 along the movable platform sliding groove.

[0025] In the present application, all the branched chains are identical and equal in length, the top end of each branched chain is connected to the moving platform 5 based on a moving pair, and the bottom end is connected to the fixed base 6 based on the bottommost rotating pair; the fixed base 6 is a cross structure, a star structure or a circular ring structure, and the specific structure is selected according to actual needs. The branched chains are uniformly arranged on the circumference formed by the connection points of the bottom ends of the branched chains and the fixed base 6. In the present embodiment, the fixed base 6 is a cross structure with equal length branches, the four branched chains are symmetrically arranged in pairs, and are uniformly arranged on the circumference of the circumscribed circle of the cross structure.

[0026] In the present application, the intersection of the rotation axes of the bottommost rotating pairs of the N branched chains is the telecentric point. As shown in Figure 8 、 Figure 9 and Figure 10 , the motion axes of the first rotating pair 1-1 of the first branched chain, the first rotating pair 2-1 of the second branched chain, the first rotating pair 3-1 of the third branched chain and the first rotating pair 4-1 of the fourth branched chain always intersect at a point and each axis is in the same plane, and the point is the telecentric point.

[0027] The driving pairs include driving pairs for moving platform transformation and driving pairs for branched chains; the moving platform driving pairs include: N moving pairs; that is, in the present embodiment, the four moving platform moving pairs: moving pair one 51-2, moving pair two 52-2, moving pair three 53-2, and moving pair four 54-2 are set as driving pairs for controlling the configuration change of the reconfigurable moving platform. In actual application, linear driving modules such as linear cylinders are used for driving to realize the displacement change of the moving pairs. The driving pairs for branched chains include: the first rotating pair and the second rotating pair on each branched chain, which are driven by motors to realize rotation.

[0028] By adjusting the positional relationship of the fifth rotating pair at the top end of each branched chain and the moving platform 5, the mechanism can be controlled to enter different telecentric motion modes. The mechanism of the present application supports three different motion modes, which are: three rotating and one moving 3T1R with a fixed telecentric point, two rotating and one moving 2T1R with a fixed telecentric point, and one rotating and one moving 1T1R with a fixed telecentric point.

[0029] The initial state of the mechanism of the present application is the motion mode of three rotating (R) and one moving (T) with a fixed telecentric point, in which mode, among the four moving platform links of the reconfigurable moving platform 5, the ends of all the branched chains coincide with the center of the reconfigurable moving platform in the plane of the moving platform. As shown in Figure 8The illustrated embodiment shows four reconfigurable moving platform links 5 connected layer by layer. The axes of the rotating joints of the four moving platform links are on the same straight line L. The axes of the fifth rotating joints of the four branches L1, L2, L3, and L4 coincide with axis L. In the figure, the red arrows represent the three rotating axes of the moving platform 5 in this mode: R1, R2, and R3. The blue arrows indicate the movable direction T of the moving platform 5. The movable direction T is located on the circumferential line L and coincides with one of the rotating axes R.

[0030] exist Figure 8 As shown in the 3T1R configuration with a fixed telecentric point, by driving the first revolute joint 1-1 of the first branch, the first revolute joint 2-1 of the second branch, the first revolute joint 3-1 of the third branch, the first revolute joint 4-1 of the fourth branch, the second revolute joint 1-2 of the first branch, the second revolute joint 2-2 of the second branch, the second revolute joint 3-2 of the third branch, and the second revolute joint 4-2 of the fourth branch, the mechanism achieves a motion mode of three rotations and one movement with a fixed telecentric point. For example, by driving the first revolute joint 1-1 of the first branch, the first revolute joint 2-1 of the second branch, the first revolute joint 3-1 of the third branch, the first revolute joint 4-1 of the fourth branch, and the second revolute joint 2-2 of the second branch, the second revolute joint 3-2 of the third branch, and the second revolute joint 4-2 of the fourth branch to rotate simultaneously in the same direction, the moving platform 5 can achieve rotation in the R3 direction with L as the axis. Drive one or more of the following components to rotate: the first branch second revolute joint 1-2, the second branch second revolute joint 2-2, the third branch second revolute joint 3-2, and the fourth branch second revolute joint 4-2, while locking the first revolute joint, thus enabling movement in the T direction.

[0031] The second state of the mechanism in this application is a motion mode of two rotations and one movement with a fixed telecentric point. In this mode, on the plane of the moving platform, the end of the fourth link of at least one branch does not coincide with the center of the reconfigurable moving platform, that is: at least one axis of L1, L2, L3, L4 does not coincide with axis L, but at the same time, all four axes L1, L2, L3, L4 are perpendicular to the plane of the fixed platform. For example, based on Figure 8 In the initial state, the moving joints on the four moving platforms are driven, causing the cylindrical sliders at the top of all branches to slide along the sliding grooves of the moving platform, moving away from the center point of the moving platform 5. Then, the axes L1, L2, L3, and L4 of the fifth rotating joints of the four branches separate from axis L, entering the 2R1T mode. Figure 9 The state of the illustrated embodiment. Figure 9In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point. Figure 9 In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point.

[0032] In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point. Figure 9 In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point. Figure 10 In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point. Figure 10 In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point. Figure 10 In the state shown in FIG. 6, the four moving platform connecting rods of the reconfigurable moving platform 5 are connected layer by layer, and the axes of the four moving platform connecting rods are the same straight line L. At this time, the fifth rotating pair axes L1, L2, L3 and L4 of the four branches are all not coincident with the axis L, and the four axes L1, L2, L3 and L4 are all perpendicular to the plane where the fixed platform is located. At this time, by driving the first rotating pair and the second rotating pair on each branch, the mechanism realizes the motion mode of two rotations and one translation with a fixed telecentric point.

[0033] After using the technical solution of the application, all the branched chains are completely connected in parallel between the moving platform 5 and the fixed base 6, and the RCM is realized by relying on the constraint relationship between the branched chains, and the degree of freedom can be changed according to the change of the end of the branched chain. The degree of freedom of the parallel mechanism is the intersection of all branched chains, and the normal direction of the moving plane and the rotation center play an important role when the moving and rotating motions of different branched chains intersect. The patent utilizes the change of the position of the rotation center of the branched chain to realize the switching of different degrees of freedom. For example, when the degree of freedom is 3R1T, the rotation centers of all branched chains coincide at this time. For example, when the degree of freedom is 2R1T, the rotation centers of the branched chains do not coincide, and are all perpendicular to the plane where the fixed platform is located. For example, when the degree of freedom is 1R1T, the rotation centers of the branched chains do not coincide, and are all not perpendicular to the plane where the fixed platform is located. At the same time, the parallel mechanism in the application is connected by multiple independent kinematic chains (branched chains) to the moving platform and the static platform to form a closed loop structure. The load is shared by multiple branched chains, the overall stiffness is high, no multi-degree-of-freedom motion pair is used, but only the rotating pair and the moving pair can realize the RCM, the branched chain structure is simple, easy to manufacture, and can be applied to more application scenarios.

Claims

1. A three-mode RCM parallel robot mechanism having three modes of motion comprising: The fixed base and the movable platform are characterized in that: the fixed base and the movable platform are connected through N parallel chains, wherein N is greater than or equal to 3; all the chains have the same chain structure, which is an RRRRR chain; The movable platform comprises N equal-length movable platform links; the movable platform link is a plate structure, and a through slot is arranged in the middle as a movable platform sliding groove; at least one end of the movable platform link is provided in a circular arc shape; the upper surface of the circular arc end is provided in a circular arc shape and protrudes upward and is perpendicular to the plate surface of the movable platform link along the arc of the end; meanwhile, the lower surface of the circular arc end is provided in a concave circular arc sliding groove along the arc of the end; the shape and size of the circular arc sliding groove are adapted to the shape and size of the circular arc slider; The movable platform comprises N movable platform rotating pairs and N moving pairs; N movable platform links are inserted together from top to bottom based on the circular arc sliding groove and the circular arc slider, and constitute N coaxial movable platform rotating pairs; The top end of each chain is connected to the movable platform based on a moving pair, and the bottom end is connected to the fixed base based on the bottom rotating pair; the chains are uniformly arranged on the circumference formed by the connection points of the chain bottom ends and the fixed base; The intersection of the rotation axes of the bottom rotating pairs of the N chains is a telecentric point.

2. The RCM parallel robot mechanism with three motion modes according to claim 1, characterized in that: The chain structure comprises four chain links connected in sequence from bottom to top: a first link, a second link, a third link and a fourth link; One end of the first link forms a first rotating pair with the fixed base, the other end forms a second rotating pair with one end of the second link, the other end of the second link forms a third rotating pair with one end of the third link, the other end of the third link forms a fourth rotating pair with one end of the fourth link; the other end of the fourth link is provided with a protruding cylindrical slider, and the diameter of the cylindrical slider is adapted to the size of the movable platform sliding groove arranged on the movable platform link; the cylindrical slider is movably inserted into the movable platform sliding groove, and forms a moving pair of the movable platform and also forms a fifth rotating pair of the chain; The rotation axes of the second rotating pair, the third rotating pair and the fourth rotating pair are parallel to each other; The rotation axes of the first rotating pair and the fifth rotating pair are not parallel to each other and not collinear; meanwhile, the rotation axes of the first rotating pair and the fifth rotating pair are perpendicular to the rotation axes of the second rotating pair, the third rotating pair and the fourth rotating pair, respectively.

3. The RCM parallel robot mechanism with three motion modes according to claim 1, characterized in that: The rotation axis of the movable platform rotating pair is perpendicular to the plane where the movable platform is located.

4. The RCM parallel robot mechanism with three motion modes according to claim 2, characterized in that: It also comprises a driving pair, wherein the driving pair comprises a movable platform driving pair and a chain driving pair; The movable platform driving pair comprises N moving pairs; The chain driving pair comprises the first rotating pair and the second rotating pair on each chain.

5. The RCM parallel robot mechanism with three motion modes according to claim 2, characterized in that: The structure of the first link comprises a ring-shaped connector, a one-letter connector and a rod body; the one-letter connector is arranged at one end of the rod body in a direction perpendicular to the rod body; the ring-shaped connector is arranged at the other end of the rod body; the axis of the ring-shaped connector is perpendicular to the rod body and the one-letter connector.

6. The RCM parallel robot mechanism with three motion modes according to claim 2, characterized in that: The mechanism of the second connecting rod and the third connecting rod is the same, which comprises a U-shaped connector, a straight-shaped connector and a rod body, one end of the rod body is provided with a closed end of the U-shaped connector, two open ends of the U-shaped connector are provided with through holes in a direction perpendicular to the rod body, the straight-shaped connector is arranged on the other end of the rod body in a direction parallel to the axes of the two through holes, and the diameter of the straight-shaped connector is adapted to the inner diameter of the through hole.

7. The RCM parallel robot mechanism with three motion modes according to claim 2, characterized in that: The fourth connecting rod further comprises a rod body and a U-shaped connector, one end of the rod body is provided with a closed end of the U-shaped connector, two open ends of the U-shaped connector are provided with through holes in a direction perpendicular to the rod body, and the sliding block is perpendicular to the rod body and the axes of the two through holes.

8. The RCM parallel robot mechanism with three motion modes according to claim 1, characterized in that: The fixed base is a cross structure, a star structure, a frame structure or a circular ring structure.

9. The RCM parallel robot mechanism with three motion modes according to claim 2, characterized in that: A U-shaped connector is arranged on the fixed base, a closed end of the U-shaped connector is connected to the fixed base, two open ends of the U-shaped connector are provided with horizontal shafts in a direction parallel to the plane on which the fixed base is arranged, and the diameter of the horizontal shaft is adapted to the inner diameter of the annular connector on the first connecting rod.

10. The RCM parallel robot mechanism with three motion modes according to claim 1, characterized in that: The number N of the branched chains is 4.

Images